The present invention is an improvement over the Centralized Traffic Control System for Railroads disclosed in U.S. Pat. 3,836,768 to Clarke et al. The disclosure of that patent is incorporated herein by reference.
The referred to Clarke et al patent discloses a centralized traffic control system for railroads which includes a central office from which a railroad territory may be controlled. The central office includes a display, which as disclosed may include one or more CRT displays for displaying traffic conditions along the railroad territory, means for designating operator initiated control requests, such as a keyboard for operator entry of operator selected control requests, communication equipment connecting the central office with a plurality of field stations for the transmission of controls and the reception of indication. At the hub of the control office is a digital computer which is appropriately programmed to accept operator designated control requests, check the validity of those control requests against the status of the field traffic conditions and transmit as controls those control requests which are valid in light of actual field conditions. The computer also drives the CRT displays so as to display the status of field conditions at a selected location in the territory. The control system which comprises the aforementioned Clark et al system is based on the CTC (unit lever) type operation in which the operator designates a particular track switch or particular signal and furthermore designates the condition to which that element is to be controlled. That is, the operator may designate a particular switch and determine that the switch should be in the reverse position, and correspondly he may designate a particular signal to be cleared in a particular direction.
Another method of railroad control, which cannot be implemented with the Clark et al control system is generally referred to as NX. In the NX method of operation the operator may designate an entrance location, which is usually a signal in the railroad territory, and an exit location which also is generally another signal in the railroad territory. The control system then determines at least one possible route for a train traveling between the designated entrance and exit locations and properly lines the track switches in the route and clears the appropriate track signals. Although this method of operation cannot be implemented by the Clark et al control system other prior art systems can implement this method of operation. These prior art systems are generally characterized by the use of relay logic. The advent of the digital computer and the associated technology has made it desirable to implement the NX method of railroad traffic control using the expanded logical capabilities of the digital computer technology. It is thus one object of the present invention to provide a control system for controlling a railroad territory with the NX method of operation employing digital computer technique with the advantages flowing therefrom.
One of the advantages of employing digital computer techniques is the expanded logical capabilities of the system. In any complex railroad territory the NX method of operation is decidedly simpler for the operator in that he merely has to designate an entrance and exit location and need not concern himself with the particular switches and signals between the entrance and exit locations. In the CTC (unit lever) type of operation, as exemplified by the Clarke et al system the operator would have to designate the particular configuration for each track switch in a route and designate a control to clear each track signal in the route.
Furthermore in the NX method of operation there may be a plurality of routes between the selected entrance and exit points. Although some of these possible routes may be prevented by reason of traffic conditions in the field there still may be more than one available route between the entrance and exit locations. The use of digital computer techniques allows the system to select a preferred route, based on preestablished priorities thus enabling preferred route to be automatically selected over other routes which are not preferred.
It is therefore another object of the present invention to provide a railroad traffic control system which operates in the NX method of operation and which will select a preferred route where more than one possible route is available.
The Clark et al system illustrates a control system which employs a CRT display so as to display, to the operator, field conditions including the operated position of the track switches, the condition of the track signals, pending controls which have been transmitted but not yet executed and the occupied condition of sections of track. In an effort to increase the efficiency of railroad operations railroad managements have a desire to monitor the position of particular identified trains. This requires a control system with the ability to designate particularly identified trains and, more important, to track these trains regardless of the direction of their movement and which can cope with the possibility that a particular train may split into two units. With this capability then not only can an operator identify the position of particular identified trains but a record can be made of the movement of the train through the railroad territory for a later use.
Therefore, it is another object of the present invention to provide a railroad control system which has the ability to track particularly identified trains regardless of the movement of the trains, in a forward or reverse direction.
In the Clark et al system control requests which had been entered by the operator, had been checked and found valid, and had been transmitted are selectively displayed on the CRT so as to enable the operator to determine which of the controls he had designated has not yet been executed in the field, although transmitted from the control office. However, this capability is available in the Clark et al system only when the location to which the controls had been directed is being displayed. However, it may be important to the operator to know if controls which had been transmited, have not been executed in the field, regardless of whether or not the particular location to which these controls had been transmitted was continuously being displayed. The lack of execution of these controls may indicate a failure condition in the communication system or in the field and, obviously, this information may be very significant to the operation of the railroad.
It is therefore another object of the present invention to provide a control system for operating a railroad which monitors controls which have been transmitted and provides an indication to the operator when these controls have not been executed within a predetermined time so that the operator may investigate the cause for the failure of execution.
Another corollary of the NX method of operation is that once a route has been selected and controls clearing that route have been transmitted and executed no element in that route may be employed in a conflicting route. That is, each of the elements become protected by the control system. However, as the train for which this route has been selected and cleared traverses the route, those elements in the route behind the train should now be available for other routings inasmuch as they are no longer necessary for the route that had previously been set up. In the aforementioned Clark et al system the operator can determine, by monitoring the CRT display the positions of trains in the territory and thus the availability of elements in the route behind any train. However, this operation obviously requires operator attention and prevents the operator from performing other tasks in that he is required to monitor the display.
It is therefore another object of the present invention to provide a control system for operating a railroad in which conflicting routes may be entered by an operator. Since the routes are conflicting only one of the routes will be effected in the field. The other route or routes will be maintained pending by the control system, and, as the control system, monitoring the travel of a train through a route detects that elements behind the train are available for the previously conflicting route, these elements will be automatically incorporated into the second route and controls to make this effective will be transmitted and executed in the field. None of this operation therefore requires operator attention.
The Clarke et al control system is also characterized by a decision table type processor which is enabled to determine the validity of control requests in light of field conditions. In more detail, the processor of the Clarke et al system comprises a decision table, unique for each field station, which determines what inquiries to make and where the relevant information can be found in order to determine whether or not a particular control request is proper. Since each of the decision tables is unique to any field station any alteration in the field station requires a concommittment alteration to the decision table. However, since the respective field stations are not independent of one another, alteration of one field station may require alteration of decision table not only for that field station but for associated field stations as well. For this reason, variations to the Clark et al control system may be difficult, time consuming and therefore expensive.
It is therefore another object of the present invention to provide a control system which includes both dynamic and static storage components. The dynamic storage components are definitive of the operated conditions of the various railroad elements (such as track section occupancy, track switch position and track signal condition) which make up the railroad, the controls which have been transmitted to the respective railroad elements and the internal status of the element in the processing regime. A static storage portion is provided which is definitive of the railroad elements and the relationship there between. The dynamic and static storage portions corporate with a novel processor means in order to determine whether or not the particular control request is or is not valid in light of actual field conditions. More particularly the processor is independent of the railroad configuration so it need not be altered when field modifications are made. To reflect field changes it is only necessary to alter the static storage elements that correspond to the changed elements. In line with the forgoing, and for purposes for making the terms used in this description clear and definite the following definitions will apply:
Availability - A term applied to each element of a route, an element is deemed available if it has not been selected by another active route, see definitions of railroad element and select,
Blocking - One of a number of internal controls, i.e., controls which are not transmitted to the field; this control simulates a selected element such that the element is not available for use in any route, typically blocking would be employed when maintenance was underway on an associated element, see definitions of controls, railroad element and select,
Communication Systems - A system for completing the communication link between the central office and each of the remote field stations, the function of the communication system is to assemble controls into a message, address that message to the designated field station and transmit the message, receive indications from each of the field stations, properly schedule transmission, detect communication failures, effect communication retries and signal when indications received from the field indicate that conditions from that field station have changed from a previously received indication, although there are wide variety of communication systems which could be used, one example of the communication system which can be employed is disclosed in the co-pending Dansbach et al application Ser. No. 516,849, filed Oct. 21, 1974 and the Pulverenti et al application Ser. No. 524,901, filed Nov. 18, 1974., see definitions of controls and indications,
Control - An order for the repositioning of a track switch or the reconditioning of a track signal in the field, which has been checked by the system and found valid in the light of existing field conditions, generally a control is immediately transmitted to the field and thus those controls which have not yet been transmitted are immediately awaiting transmission, see the definition of valid,
Control Request - A request originating at the central office, requesting a variation in the condition of traffic controlling railroad elements in the field, a CTC type of control request is a request for variation in the condition of a track signal or a variation in the position in the track switch or a combination of the foregoing, and NX type request is a request for clearing a route between the designated entrance and exit locations, in the course of operating with NX type of request the system of our invention generates pseudo CTC type request which are necessary to the route, see the definitions of the route,
Common Element - A railroad element which is common to a route which has been selected and is also included in a requested route, see the definition of select and railroad element,
Dynamic Data or Dynamic Information - That class of information which is expected to change in the ordinary course of operations, examples of dynamic information are controls or indications or any of the data stored in the high Q, low Q and recall,
Entrance Location - A location in the railroad territory which may be the beginning of a route, generally a entrance location is an inline signal,
Exit Location - A location in the railroad territory which may comprise the exit of a route, generally an exit is an inline signal,
High Queue - A memory area in which data is stored, beginning at a predetermined location, which includes a representation of every route in which controls have been conditioned but for which indications have not yet been received that the conditioned controls have become effective in the field, see the definition of indications, control,
Indication - Information received via the communication system which originated at a field station indicating a present condition of a track signal, track switch or the occupancy or non-occupancy of a track section,
Low Queue - A data storage area beginning at a predetermined location in which is stored representation of all routes which include an element common to another route which has been set up in the field, the identification of the common element is included,
Railroad Element - A physical piece of apparatus, the plurality of which make up the operating plant of the railroad, in this application we will be concerned with track switches, track signals and track sections as railroad elements,
Recall or Recall Directory - A storage area beginning at a predetermined location which includes stored data of all routes which have been set up in the field and which are waiting passage of a train for which the route has been set up,
Recall Word - A separate storage area for each railroad element in which can be stored identification of the next railroad element in a route which has been, or may be set up,
Route or Routing - A route is a connected plurality of railroad elements between an entrance location and an exit location, routing also includes a conditioning of controls for proper positioning of track switches which may be included in the route,
Select or Selecting - Appropriately storing a designation for each element which is to be included in a route for protecting that element from being included in any other route,
Slotting - A procedure whereby railroad elements included in a route become available for other routes after a train has moved passed the railroad element,
Valid or Validity - The act or result of determining from a particular control request and the field condition whether or not the control request would result in any potential unsafe conditions, when a control request is deemed valid appropriate controls may be conditioned for transmission to the field, for instance, a control request for a route would be considered valid if none of the elements have been selected and if all switches can be thrown to the position necessary to make the route.